The water cycle is a global cycle because there is a large reservoir of water in the atmosphere as well as in the hydrosphere, especially in the oceans.

Obviously, the water cycle is critical to life on earth. The Water Cycle The water cycle is powered by energy from the sun and involves three major processes - evaporation, precipitation, and transpiration. SURFACE RUNOFF Water Purification CHEMICAL REACTIONS INVOLVED HUMAN IMPACT Evaporation of water from oceans, lakes, rivers, soil, and other water sources is caused by incoming solar energy. This process changes liquid water into water vapor in the atmosphere .

Gravity draws the water back to the Earth's surface as precipitation. EVAPORATION Precipitation includes rain, snow, sleet, hail, and dew.

We all know what this is. Water falling from the sky in some shape or form. PRECIPITATION This is the process in which water is absorbed by the root systems of plants, moves up through plants, passes through pores, or stomata, in their leaves or other parts, and EVAPORATES into the atmosphere at water vapor.

About 90% of the water vapor in the atmosphere that comes from land (80% comes from the oceans) is due to transpiration. TRANSPIRATION Most precipitation becomes surface runoff. This water flows into streams and lakes, which eventually carry water back into the ocean, form which it can evaporate and repeat the water cycle. SURFACE WATER Also seeps into the upper layers of soils and some evaporates from soil, lakes, and streams back into the atmosphere. Some precipitation is converted into ice that is stored in glaciers, usually for long periods of time.

Some precipitation sinks through soil and permeable rock formations to underground layers of rock, sand, and gravel caled aquifers, where it is stored as groundwater Surface runoff replenishes rivers and lakes, but it also causes soil erosion, sculpting the earth's landscape.

Becuase water dissolves many nutrient compounds, it is a major medium for transporting nutrients within and between ecosystems. Natural processes in the water cycle purify water.

Evaporation and precipitation act as a distillation process to remove impurities dissolved in water.

Water flowing above ground through streams and lakes as well as under ground in aquifers is filtered.

Water is simply water throughout the entire cycle, but there are some processes in the water cycle that involve chemical reactions Photosynthesis: when plants synthesize organic compounds from CO2 and H2O using light energy.

6CO2 + 6H2O + (light energy) = C6H12O6 +6O2

In underground aquifers, water is partially purified chemical and biological processes - mostly by actions of decomposer bacteria - as long as these actions are not overlaoded. 1. We withdraw large quantities of freshwater from streams, lakes, and underground sources, sometimes at rates faster than nature can replace it.

2. By clearing vegetation and covering the land with buildings, asphalt, and concrete, we increase runoff, reduce infiltration that would normally recharge groundwater supplies, increase the risk of flooding, and accelerate soil erosion. Clearing vegetation also reduces transpiration, which is extremely important in dense tropical rainforests where the plants "make their own rain."

3. We increase flooding by draining wetlands for farming and other purposes. Wetlands serve as natural flood control, acting as sponges to take in overflow of water from heavy rain or melting snow. Also, by covering the earth with roads and buildings we lessen the surface area for water absorption.

4. Water pollution is also caused by humans in many ways, including smog and improper waste disposal. When acid rain occurs it is very evident that our pollution affects the water cycle. By conserving and taking care of the water you have.

Never litter, your trash could make its way to our lake, and then even to our oceans.

Take little steps to conserve water in your home. Take shorter showers.Flush less: if it's yellow let it mellow, if it's brown flush it down!Mow your lawn less, taller grass holds in water better than shorter grass does. Place a bucket in your shower to capture the water that runs while you’re waiting for it to get hot. Use the water to water plants.

HOW CAN YOU MAKE A DIFFERENCE?? These and many other small steps are easy ways to conserve our water supply.